1. Field of the Invention
The present invention relates to a wall anchor device, and more particularly to a self-drilling wall anchor device having an expandable and threaded structure for solidly engaging or securing to wall members or the like and for ensuring the operation of the self-drilling wall anchor device.
2. Description of the Prior Art
Various kinds of typical wall anchor devices have been developed, and comprise a threaded fastener threaded in an expandable outer casing, to expand the outer casing and thus to engage and secure the wall anchor devices to wall members or the like.
For example, U.S. Pat. No. 5,147,166 to Harker discloses one of the typical wall anchor devices comprising a threaded bolt threaded in an expansible body element, to expand the expansible body element and thus to engage and secure the wall anchor devices to wall members or the like.
The expansible body element includes a number of connecting bands bowed slightly outwardly in the provision of angularly inclined legs. However, similarly, the angularly inclined legs of the expansible body element include a planar outer surface and may only be bent, but may not be forced to engage into the wall members, such that the typical expansible body element may not be solidly secured or anchored in blind holes of wall members.
U.S. Pat. No. 5,690,454 to Smith discloses another typical wall anchor device which comprises a threaded bolt threaded in an expansible screw anchor to expand the expansible screw anchor and thus to engage and secure the wall anchor devices to wall members or the like. However, similarly, the expansible screw anchor includes a planar outer surface and may only be bent, but may not be forced to engage into the wall members, such that the typical expansible screw anchor also may not be solidly secured or anchored in blind holes of wall members.
U.S. Pat. No. 6,065,918 to Adams discloses a further typical wall anchor device which comprises an insert having a drilling blade for drilling into wall members or the like, and a threaded bolt threaded into the insert to expand or bend the blade laterally or outwardly, and thus to engage and secure the wall anchor devices to wall members or the like. However, the insert of the typical anchor device includes a planar outer surface and may not be expanded and thus may not be solidly secured or anchored in blind holes of wall members.
In addition, in the typical wall anchor devices, the typical expansible sleeves or body elements are normally made of plastic materials which may be slightly expanded due to a hot weather or in a humid environment and may be shrunk due to a cold weather such that the inner threaded bolt may not suitably engage with the expansible sleeves or body elements in the hot weather and may be tightly engage with the expansible sleeves or body elements in the cold weather and such that the expansible sleeves or body elements may not be suitably expanded or twisted or deformed by the inner threaded bolt.
Furthermore, the inner threaded bolts and the expansible sleeves or body elements of the typical wall anchor devices have no locating or positioning device or structure provided thereon such that the expansible sleeves or body elements may not be timely expanded or twisted or deformed by the inner threaded bolt according to different thickness of the work pieces.
The present invention has arisen to mitigate and/or obviate the afore-described disadvantages of the conventional wall anchor devices.